Hard Science Fiction - A problem of Definition

Hard Sci Fi can sometimes be difficult to define, because different people have different interepretations of the trem. A good definition of Hard SF would be that branch of Science Fiction in which the events in the story could conceivably happen in the universe as we know it, the science and technology as plausible as possible, and that there no (or at least very few) glaring errors of fact, such as could easily be checked using standard reference material. Soft SF is the opposite. For more on this definition see On Hard SF.

Another, older definition might be that Hard SF is that branch of literature which is written with science or technology as the main focus of the story. Whereas Soft SF is about social, psychological, or humanistic issues. In this definition Hard and Soft SF are complementary rather than contradictory, as there is no reason why a story written with science tech as the focus, or just simply a scientifically viable story, cannot have good character development as well. See also Libertarianism and the Hard SF Renaissance (you have to scroll down the page somewhat) for a good review of Hard (Campbellian) vs Soft ("New Wave") SF)

Both of these definitions dates back to John W Campbell, who in 1938 took over editorship of the "pulp" magazine Astounding, which up until then had been only publishing stories of Bug Eyed Monsters wanting to ravish Earth maidens, and other such nonsense, and introduced scientific rigor and higher standards.

Despite its attempt at scientific rigor, almost all so-called Hard SF includes things that are against the known laws of physics, such as FTL drive, or conflicts current empirical evidence, such as a galactic culture teeming with civilizations (even though these have not been detected by current astronomers or SETI). Soft Sci Fi (such as Hollywood movies and well known sci fi franchises) is even more unrealistic. In formulating a created universe like, say, Orion's Arm, we have tried to be as strict as possible, but at the same time not so strict as to stifle the imagination. This has meant a necessary balance between Near Future Ultra Hard (or Diamond Hard) type Science Fiction, and more mainstream SF. It was therefore decided not to use many tropes that are standard even for much of mainstream SF (FTL without time travel paradoxes, humanoid aliens, psi-empaths, etc). While this may seem to be restrictive, in fact it is not, as the richness of this setting shows.

However it is quite obvious that not all of what is considered as "true and proven" now will remain so in another 10 millenia! In this regard, "hard science", certainly does not have to be the same as "ultra hard" or "diamond hard". We can no more predict the future accurately than people in ancient Greece 500 b.c.e. could predict or envisage the science and technology of today. Ok, being rational, they could make some educated guesses. And ultimately that's also what we're doing here. Hence we try to balance Only What Is Known By Today's Science with What Might Be Possible Speculating From Here. We avoid things that are known to be ridiculous, or impossible, but if it is reasonably plausible, or possible, but not yet certain, we can include it.

See also Hard vs Soft SF Scale for further definitions of Hard SF and distinction and gradation between "hard" and "soft" science fiction

Soft Sci Fi Soft Sci Fi is also the opposite of what we define here as Hard Sci Fi; it is not the same as Soft/Literarly/Social Science SF, but refers to scientifically unrealistic pop media sci fi